Mounting an ER collet chuck

HI when mounting this er collet chuck onto a backplate. Should the register be cut deep so the chuck mounts with the central lower face in contact with the backplate. Or shallow so the bolting outer face contacts the backplate. Or maybe it doesn't matter.

Thanks Rich

My choice would be for the register to be a little shallower than the recess in the collet chuck, but a snug fit on the OD, (otherwise there is no point in having it )

Howard

Find out which is the concentric register and use that one. Sometimes the outside is more cosmetic than functional, ie not done at the same time as the 2 inner diameters.

What ever clearance is on the register is the permissible error in mounting each time. One way around this is to make it with some small amount of interference or as measured size for size. Then use castor oil to aid in the assembly. It will require some form of extraction to remove, but will be the most concentric that you can have , apart from matching precision tapers.

Neil

How would one find out which is the concentric register?

I can only see one feature in the picture that I would call the register and its the large diameter surrounded by the bolting face. The spigot on the backplate should be a tight fit to that recess and the spigot 'length' less than the depth so that face to face contact is on the bolting face.

Since Richard is mounting this on a backplate I dont see why the permissible error would re occur

Ian P

Thanks

Are these registers definitely the way to get the best concentric fit? Is that how they are made? Is it a ridiculous idea to just nip it up and then gently tap it across in a similar way to moving something onto centre in a four jaw chuck.

Yes you can do that as an alternative. It all depends on how you set up and how often it is being removed and replaced etc.

You cut the spigot on your backplate, while the backplate is mounted on the lathe in its normal operating position to ensure concentricity with your lathe spindle.

You bought a collet chuck which should have all machined surfaces concentric.

There are spigots for a reason. Use them is my advice to accurately locate the parts precisely and concentrically.

Cut on your lathe, there will be no run-out attributable to the backplate. If the er chuck runs out, when fitted snugly/tightly to the spigot, it was a carp product.

Ian P has it listed perfectly, for the machining requirements. Follow that and it should work (provided the collet chuck is up to scratch).

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I agree 100% with your principle ... but those provisos remind me of the wise old saying:

"If you can't make it right, make it adjustable" [*]

MichaelG.

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[*] and in this instance that might translate to:

"If you can't buy parts that they made right, you may need to make your interface adjustable"

Edited By Michael Gilligan on 29/06/2019 09:10:14

Agreed. It may depend on the origin of one’s purchase. Bang good comes immediately to mind for that scenario. Buying from a supplier that has good quality control and stands by their product is a different situation than purchasing cheap chinese products that were likely already rejected by those with high quality control standards.

Not using that spigot as a register is already less than a satisfactory situation. In that scenario, the spigot might just as well not exist at all!

“ Or shallow so the bolting outer face contacts the backplate.”

Just that Rich!

Rik

Hi, chuck a suitable piece of round bar long enough to mount the collet chuck onto. Turn the bar true and parallel to fit the largest collet and without removing the bar, mount the collet chuck back to front onto the bar. Measure all the faces and registers with a DTI, if it's good, then the measurement should be within the tolerance stated.

Regards Nick.

P.S. I would use the face with the bolt holes in, for the mounting face and leave a gap between the recessed face.

Edited By Nicholas Farr on 29/06/2019 10:21:13

I'm sure the advice above is perfectly sound but I didn't try for a perfect register fit on either of my ER32 backplates. They were machined slightly over size - the chuck mounted and then clocked true and then the screws tightened up. There shouldn't be any run out if done as suggested I agree - but that's how I did it mine, they run true and they haven't shifted in use.

Regards,

IanT

Edited By IanT on 29/06/2019 10:20:54

Hi IanT, I was confident that the collect chuck that I purchased was accurate, I did much the same as you did and when fitted and checked, proved to run true.

Regards Nick.

I have one of those collet chucks, I machined the backplate to fit the inside of the register quite tightly. The runout was less than 0.01mm which was fine for me.

Well armed with all your advice I went out and cut a register that was just a little tight and a little shallower than the recess in the chuck. I then pulled it up onto the bolting face using the bolts. With a Verdict indicator on the internal taper it moves with the slightest sway about 0.0002 inch. If anyone is interested the chuck came from Arc and the camlock backplate from Rotagrip.

Thanks to all of you who gave advice.

Rich